Diabetes mellitus (DM) leads to a 3-4 fold higher risk of experiencing ischemic stroke. Hyperglycemia and diabetes instigate a cascade of events leading to vascular endothelial cell dysfunction, increased vascular permeability and poor recovery after ischemic stroke. Diabetic animal's exhibit more severely injured white matter (WM) than non-DM animals after stroke. There is also a differential response to treatment of stroke between DM and non-DM subjects. Effective therapy of stroke in the non-DM population may not necessarily transfer to the DM population, prompting the need to develop therapeutic approaches specifically designed to reduce neurological deficits after stroke in the DM population. Our preliminary data show that T2DM significantly decreases microRNA-126 (miR-126) and Angiopoietin-1 (Ang1) expression in the circulation and in the ischemic brain of mice. Human umbilical cord blood cell (HUCBC) treatment of stroke in T2DM mice starting at 3 days after stroke significantly improves recovery of neurological function as well as increases miR-126 and Ang1 expression in the ischemic brain. Therefore, based on our robust preliminary data, we propose to use HUCBCs for the treatment of stroke in the T2DM mice and to investigate the role of intercellular communication via miR-126 encapsulated within Exosomes/Microvesicles (EMVs) in mediating the therapeutic benefit on HUCBCs for ischemic stroke. This application includes three Aims. Aim 1 will test if miR-126 mediates HUCBC treatment induced neurorestorative effects after stroke in T2DM mice. We hypothesize that miR-126 mediates HUCBC treatment-induced vascular integrity, axonal outgrowth, and WM remodeling, and improves functional outcome after stroke in T2DM mice. Aim 2 will test whether miR-126 generated by HUCBCs is transferred to brain endothelial cells (BECs) and parenchymal cells via EMVs. We hypothesize that HUCBCs secrete EMVs containing miR-126 which are taken up by BECs and parenchymal cells. Aim 3 will investigate whether miR-126 regulation of Ang1 promotes the HUCBC-induced neurorestorative effects after stroke in T2DM mice. We hypothesize that: 1) HUCBC treatment of stroke in T2DM mice increases Ang-1 signaling activity in the ischemic brain; 2) miR-126 regulates Ang1 expression and thereby regulates vascular remodeling, axonal outgrowth and oligodendrocyte survival and differentiation; 3) Restoration of Ang1 with an Ang1 mimetic peptide will rescue the neurorestorative effects of knockdown of miR-126 in HUCBC after stroke in T2DM mice. In this application, we are the first to propose that, generation of miR-126 encapsulated in EMVs by HUCBCs contributes to its robust therapeutic restorative effects and that miR-126 and its regulation of Ang-1 mediate HUCBC-induced neurovascular and WM remodeling, and thereby improve stroke functional recovery in T2DM mice. This proposal is highly clinically relevant and if successful, will significantly impact the treatment of diabetic and possibly all stroke patients